1. Field of the Invention
The present invention relates to an access point device and a communications system, and is applicable, for example, to a method of updating terminal connection information held in a network switcher according to a handover process that is performed between access point devices.
2. Description of the Background Art
A description will be given of a conventional method in which a wireless VoIP (Voice over Internet Protocol) terminal is handed over on a wireless local area network (LAN). A plurality of access point devices are connected to some of the ports of a network switcher, one of the remaining ports being connected to an external network through a router. Note that the external network has external terminal devices connected thereto. The access point devices each has a wired-LAN interface, a controller, and a wireless LAN interface. A wireless LAN terminal device is connected to any access point device and communicates with that device.
If the wireless LAN terminal device connected to one access point device moves during communication and enters the administration area of another access point device, the wireless LAN terminal device is handed over from the previous access point device to the next access point device to be reconnected to the next access point device.
Such a handover technique between access point devices is disclosed in Japanese patent laid-open publication No. 2004-229225 by way of example.
When a wireless LAN terminal device is moving during communication and the handover process is being executed between access point devices, a frame is sometimes transferred from an external terminal device to this wireless LAN terminal device. At this time, a MAC (Media Access Control) address table in the network switcher has not been updated yet. The MAC address table defines the relationship of the MAC address of a wireless LAN terminal device with a corresponding switcher port number, etc. Because of the MAC address table not updated, there may be cases where the relay of a frame to the wireless LAN terminal device is unsuccessful.
As a technique for avoiding such a case, there has been proposed a method in which the next access point device receiving a reconnection request after movement of a wireless LAN terminal device transmits a dummy data frame in which the MAC address of the wireless LAN terminal device is inserted in its destination address field, and a network switcher receiving the dummy data frame updates the connection information in its MAC address table that corresponds to the wireless LAN terminal device. In addition, for example, some conventional access point devices are equipped with a proxy address resolution protocol (ARP) function which, when receiving an ARP request for the IP (Internet Protocol) address of a destination LAN terminal device to be relayed by its own device, replies to the ARP request by proxy, in order to reduce the necessity to transmit the ARP request to the wireless LAN terminal device to be connected and reduce the power consumption of the wireless LAN terminal device.
However, in the case of adopting the above-described method in which the next access point device connected after movement of the wireless LAN terminal device transmits a dummy data frame to the network switcher, there arises a problem that this access point device has to transmit the unnecessary data frame.
In the case of utilizing the above-mentioned proxy ARP function equipped in the access point device, the access point device normally cannot use the proxy ARP function until it receives an IP packet from the wireless LAN terminal device connected thereto.
Therefore, even if frames are transmitted from an external terminal device to the wireless LAN terminal device, in the access point device the proxy ARP function cannot be executed until it receives an IP packet from the wireless LAN terminal device and identifies the IP address of the wireless LAN terminal device, and consequently, there will arise another problem that frames cannot be relayed.
In addition, the handover source, that is, the previous access point device continues to have the proxy ARP function of the wireless LAN terminal device which is no longer located within its administration area. Because of this, the previous access point device sometimes replies to an ARP request. This replay gives rise to ARP inconsistency, whereby there is a possibility that trouble will occur in the operation of the entire network.